Electric circuit breaker with break-away coupling



Dec. 9, 1969 R. L H-URTLE 3,483,4

ELECTRIC CIRCUIT BREAKER WITH BREAK-AWAY COUPLING -Fi led Aug, 19, 1968'ZSheets-Sheet 1 4' EV 74 Z 38 9a 60 y g 22 42 AH 75 Z6 I f 36 u 9Z3. mz

34 19 U m 25 32 \i 46 8: 20 44 58 96 4 40 83 /0- 54 I 4 M/Vwmk RALPHLI/I/RHE BY awm R. L. HURTLE '1 Dec. 9,1969

ELECTRIC CIRCUIT BREAKER WITH BREAK-AWAY COUPLING 2 Sheets-Sheet 2 FiledAug. 19, 1968 FlG.6

lNvENroR PAL/=11 L. #02745 B WM United States Patent Ralph L. Hurtle,West Hartford, Conn., assignor to General Electric Company, acorporation of New York I Filed Aug. 19, 1968, Ser. No. 753,592 Int. Cl.H01h 75/00 US. Cl. 335--6 13 Claims ABSTRACT OF THE DISCLOSURE A circuitbreaker has a movable contact carried by a contact operating member andautomatic operating means and manual operating means for effectingmovement of the contact operating member from closed to open circuitposition. Disengageable means is provided to couple the manual operatingmeans to the contact operating member for normal operation thereof, butthe coupling means is disengageable upon operation of the automaticoperating means to permit opening movement of the contact operatingmember independently of the manual operating means. The coupling meansincludes a resiliently deflectable spiral spring member encircling thecontact operating member and seated in cooperating recesses in opposedsurfaces of two relatively movable portions of the coupling means. Thereis also disclosed means for resisting inadvertent operation byacceleration forces.

BACKGROUND OF THE INVENTION The increasing use of electric power forvarious purposes has produced a requirement for electric power supplysystems of ever increasing capacity and a concurrent requirement forcircuit breakers capable of interrupting the high short circuit currentswhich can occur in such power systems. Moreover, it has been recognizedthat it is desirable to prevent the short circuit current .fromattaining a magnitude during interruption which approaches theprospective short circuit current maximum since even the interruptedshort circuit current may cause damage to other circuit components. Thisfunction is referred to as current limiting.

As a result, special current limiting electric circuit breakers havebeen developed employing means for separating the breaker contacts byelectromagnetic forces with virtually no time lag, upon the occurrenceof a high short circuit current. A highly effective electric circuitbreaker of this type is disclosed in Patent No. 3,384,846, Heft, issuedMay 21, 1968 and assigned to the same assignee as the present invention.

As disclosed in the aforementioned Heft patent, it is highly desirableto open the contacts of the circuit breaker, as rapidly as possible,thereby drawing the are quickly. As further pointed out in this patent,operation of the moveable contact is desirably made independent ofmovement of the relatively massive elements of themanual-and-conventional-automatic switching mechanism so that theinertia of these systems do not detract from rapid opening. To this end,the Heft device includes a disengageable coupling between themanual-and-conventional-automatic operating mechanism and the contactoperating rod which has proven effective.

It is an object of the present invention to provide a current. limitingcircuit breaker which is capable of rapidly opening the contactsindependently of operation of the manual operating mechanism and whichmay be simply and economically constructed. 1

It is also an object to provide such a circuit breaker wherein theelements are normally held firmly engaged for manual operation but arereadily disengageable upon I 3,483,490 Patented Dec. 9, 1969 actuationof automatic operating means functioning in response to current of highmagnitude, such as that occurring during a short circuit condition.

Another object is to provide such a circuit breaker which may be readilyassembled and disassembled and which is capable of long lived operationand ready variation in the magnitude of current required for automaticoperation.

A further object is to provide such a circuit breaker having means forlessening the likelihood of inadvertent operation by accelerationforces.

SUMMARY OF THE INVENTION It has now been found that the foregoing andrelated objects can be readily attained in an electric circuitinterrupter having a casing containing a stationary contact and amovable contact with a contact operating member carrying the movablecontact at one end thereof. Means in the casing mounts the contactoperating member for movement of the movable contact between closed andopen circuit positions, and automatic operating means connected to thecontact carrying member provides for movement thereof from closed toopen circuit position upon passage of a short circuit current ofpredetermined magnitude therethrough. Manual operating means is providedin the casing, and coupling means connects the manual operating means tothe contact operating member for movement thereof between closed andopen circuit positions.

The coupling means includes a coupling member connected to the manualoperating means and disengageable means connecting the coupling memberto the contact carrying member. The disengageable connection between thecoupling member and the contact carrying member includes a spring memberof generally toroidal configuration encircling the contact operatingmember and being capable of resilient variation in its diameter. Theopposed surfaces of the contact carrying member and coupling member havealigned recesses therein each partially receiving the spring member inthe normal operative condition of the assembly to provide a con nectiontherebetween for operation of the contact carrying member upon movementof the manual operating means. The recess in one of the cooperatingmembers is of a depth sufficient to completely receive the spring memberas a result of sutficient expansion thereof to permit relative movementof the contact carrying member and the coupling member.

In the preferred aspect, the spring member is of the garter spring type,i.e., a spring wire coiled in a toroidal configuration. The springmember may be of either the tension type or the compression type so asto be expansible or compressible to effect the desired deflectiondepending upon the construction and dimensioning of the parts permittedin a given assembly. Accordingly, the member having the grooves orrecesses or a depth suflicient to receive the full thickness of thespring may be either the coupling member or the contact carrying member.Various other features and additional elements of construction may beutilized within the present invention for o timum operation as will bepointed out in detail hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a side elevational view ofan electric circuit breaker embodying the present invention withportions broken away to reveal internal construction and with themovable Contact member shown in the manually opehated closed circuit oron condition in full line and in the automatically operated offcondition in phantom line;

FIGURE 2 is a fragmentary side elevational view illustrating the movableelements of the circuit breaker of FIGURE 1 in the manually operated offor open circuit condition;

FIGURE 3 is a fragmentary sectional view along the line 33 of FIGURE 1;

FIGURE 4 is a longitudinal sectional view of one embodiment of thedetent mechanism of the circuit breaker of FIGURE 1 on an enlarged scaleshowing the members in normal operating or coupled condition;

FIGURE 5 is a view similar to FIGURE 4 showing the members of the detentmechanism after automatic operation;

FIGURE 6 is a transverse sectional view of the detent mechanism alongthe line 66 of FIGURE 4;

FIGURE 7 is an exploded fragmentary side elevational view of the membersthereof;

FIGURE 8 is a side elevational view of another embodiment of detentmechanism having means for compensating for accelerational forces;

FIGURE 9 is a sectional view along the line 9--9 of FIGURE 8; and

FIGURE 10 is a sectional view along the line 10-10 of FIGURE 9 andshowing in dotted line the operating eifect of the counterweight.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Turning first indetail to FIGURES 1-7, therein illustrated is a circuit breaker havingan insulating casing generally designated by the numeral 10 with sidewalls 12, 14 and a top wall 16. Mounted in the casing by suitable means(not shown) is a pair of spaced stationary contact assemblies generallydesignated by the numerals 18, and which have'opposed contact faces 22,24 adjacent their inner end and diverging arc runner portions 26, 28.Movable into and away from contact with the con a faces 22, 24 are thecontact faces 30, 32 of the generally wedge-shaped movable contactmember generally designated by the numeral 34 carried on the end of theelongated contact operating rod 36. Received between the inner endportions 38, of the stationary contact assemblies 18, 20 is a generallycup-shaped insulating member 42 which provides a pressure chamber 44about the region of movement of the movable contact member 34 and whichhas a close fitting aperture 46 in the end wall thereof in which thecontact operating rod 36 is slidable.

A line terminal 48 on the casing 10 supplies current to the conductivestrap 50 which is electrically connected to the stationary contactassembly 18 by the con- I 'coil cooperating with the arc runner portion28. At its opposite end, the conductor 56 is attached to the terminal 58of the solenoid 60 which in turn is connected to the strap 62 of theload terminal 64 by the conductor 66.

As a result, the current path through the circuit breaker is from theline terminal 48 to the strap 50 and thence through the conductor 52 tothe stationary contact assembly 18. When the movable contact member 34is in closed circuit position, the current fiows from the contact face22 to the contact face 30 of the movable contact member 34 and thence tothe contact face 24. Since the face 24 is connected by the conductor 56to the solenoid 60, the current flows therebetween and thence throughthe line 62 to the strap 66 of the load terminal.

In accordance with conventional practice, the breaker includes manualoperating means for moving the contact operating rod 36 to and fromclosed circuit position with respect to the contact faces 22, 24, whichmeans includes a manually engageable handle member 68 projectingoutwardly through an aperture 70 in the top wall 16 of the casing 10;The generally inverted U-shaped handle sup port member 72 within thecasing 10 has slots 74 in the free ends of its legs which pivotally seaton the fixed pivot pins 76 on the support brackets 80, 82 of the casing10 so as to be pivotal between the positions shown in FIG- URES 1 and 2of the drawings. A pair of offset connecting links 78 are pivoted attheir upper end by the pins 76 and have elongated slots 84 at theirlower ends which receive pivot pins 86 on the sides of the couplingmember generally designated by the numeral 88. A pair of operatingsprings are connected at their upper ends to pins on the upper portionof the handle support member 72 and at their lower ends to theconnecting links 78 to provide a toggle action.

When the parts are in the on condition shown in full line in FIGURE 1,-the line of action of the operating springs 90 lies to the left of thepivot pins 76 as viewed therein or to the side of the .pins 76 spacedtowards the contact assemblies 18, 20. This biases t connecting links 78clockwise about the pivot pins 76 and urges the coupling member 88 andthereby the contact operating rod 36 and movable contact member 34 intofirm electrical contact with the stationary contact faces 22, 24. Whenthe handle member 68 is moved to the off position shown in FIGURE 2, theline of action of the springs 90 is to the right of the pivot pins 76 asviewed therein or to the side of the pins 76 spaced away from thecontact assemblies 18, 20. This biases the operating links 78counterclockwise about the pivot pins 76 and urges the coupling member88 and thereby the contact operating rod 36 and movable contact member34 away from electrical contact with the stationary contact faces 22,24.

As best seen in FIGURES 1 and 2, the contact operating rod 36 carries asolenoid plunger 96 at its end which is slidably received in the tubularsleeve 98 fixedly mounted in the casing 10. A limited amount of slidingmovement of the solenoid plunger 96 on the operating rod 36 is providedby the mounting pin 92 which rides in slots 94 of the tubular operatingrod 36 which contains a spring (not shown) normally biasing the pin 92and thereby the plunger 96 beyond the end of the rod 36. On passage ofcurrent of a predetermined magnitude through the solenoid 60, themagnetic force of the solenoid and the rapidity of action are sufficientto disengage the releasable connection between the coupling member 88and the contact operating rod 36 and draw the operating rod 36 away fromthe contact assemblies 18, 20 to open the contact rapidly. The solenoidplunger 96 strikes against the resilient stop cushion 100 of neoprene orthe like which protects the field piece 102 of the solenoid 60. Inaddition, the rod '36 can continue to move rearwardly relative to theplunger 96 by reason of the pin and slot connection against the actionof the spring to provide for some override and damping action.

Similar provision for shock absorption upon closing of the contacts anda lost motion connection upon opening of the contacts is provided by themounting pin 104 on the plunger portion 106 of the movable contactmember 34 which rides in slots 108 in the contact operating rod 36. Aspring (not shown) in the tubular operating rod 36 biases the plungerportion 106 outwardly of the rod 36 so that upon closing of the contactssome override of the operating rod 36 and damping action is provided.Upon opening movement of the rod 36, the connection enables some lostmotion between the rod 36 and contact member 34 before the contacts areactually opened.

Turning now in detail to the embodiment of disengageable connectionbetween the coupling member 88 and the operating rod 36, this is bestseen in FIGURES 4-7 of the attached drawings. The coupling member 38 isof generally cylindrical or toroidal cross sectionwith a pair of radialbosses 110 (see FIG. 7) having the pins 86 thereon and also has a bore112 extending therethrough with a reduced diameter portion at the endadjacent the contact assemblies 18, 20 providing a circumferentialshoulder 113. An annular groove 114 extends about the innercircumference of the coupling member 88 adjacent the end closest to thesolenoid plunger 96 and is dimensioned to provide a depth suflicient toreceive the full thickness of the coiled, annular garter spring member116 which normally only partially seats therein.

The operating rod 36 has fixed thereon by the pin 118 a tubular sleevegenerally designated by the numeral 120.

A circumferential groove 122 in the member 120 is aligned with thegroove 114 of the coupling member 88 in the normal operating position asshown in FIGURE 4 and is of relatively shallow depth so as to receiveonly a portion of the thickness of the spring member 116. In thismanner, the spring member 116 provides interengagement between thecoupling member 88 and member 120. The member 120 has a reduced diameterend portion adjacent the contact assemblies 18, 20 providing acircumferential shoulder 124 between it and the major diameter portion,and this reduced end portion seats in the reduced diameter end portionof the bore 112 with the shoulders 113, 124 in abutting contact in thenormal operative position of the members.

In normal operation of the circuit breaker, the garter spring seatspartially within the grooves 114, 122 of the coupling member 88 and themember 120 of the contact operating rod 36 since the groove 122 is oflesser depth than the thickness of the spring 116. Upon rapid actuationby the passage of a short circuit current through the solenoid 60, theforce of the operating rod 36 causes the side wall of the groove 122 topress against the spring 116 and expand it in diameter until it passescompletely into the groove 114 of the coupling member 88. This allowsthe operating rod 36 to move independently of the coupling member 88 andthe remainder of the operating mechanism and thus be free of the inertiathereof. As the contact operating rod 36 moves toward the cushion 100,the spring 116 rides along the surface of the sleeve 120 until it dropsonto the reduced portion and the shoulder 124 provides an abutment toprevent the contact rod 36 from bouncing back and reclosing thecontacts.

The radius of the coils of the garter spring member 116 and its diameterand strength are selected with respect to the grooves or recesses 114,122 of the cooperating members 88, 120 so that the force exerted therebywill normally resist relative movement between the member 88 and themember 120. Operation of the handle member 68 thus will produce movementof the operating rod 36 between open and closed circuit positions.Although the solenoid 60 is exerting, a magnetic force on the solenoidplunger 96 at all times during current flow through the breaker, it isgenerally a relatively low force. In an instance of a short circuitcurrent of predetermined magnitude, however, the force of the solenoidacting on the rod 36 earns the spring 116 outwardly from the recess 122of the sleeve 120 as it draws the rod 36 axially towards the solenoid60. Although the force of the solenoid 60 under the predeterminedconditions for automatic tripping is much greater than that of theoperating springs 90, the manual operating mechanism is not moved to theopen circuit position when this occurs largely because of the inertia ofthese parts. Instead, the operating rod 36, together with the member120, the solenoid plunger 96 and the movable contact member 34 movewithout being impeded by the inertia of the elements of the manuallyoperable mechanism although the coupling member 88 remains insubstantially the same position. Although the spring 116 is deflectedand expands sufficiently to allow sliding within it of the outer surfaceof the sleeve 120, it quickly closes around the forward end of themember 120 beyond the shoulder 124 to prevent the movable contactassembly from moving back 0 rebounding toward closed circuit position.

Following automatic opening, the mechanism may be reset to permitreclosing simply by moving the operating handle member 68 to its normaloff condition, thereby returning the garter spring member 116 intoengagement in the groove 122 of the member 120. The circuit breaker maythen be reclosed by returning the handle member 68 to its on position asshown in FIGURE 1.

Turning now to FIGURES 8-10, therein illustrated is an embodiment of thepresent invention particularly suitable for use in vehicles or militaryapplications where inadvertent operation as a result of environmentalacceleration is to be avoided. In this embodiment, the generalconstruction is the same as in the embodiment of FIGURES 1-7 with thesame members being employed for unmodified elements. The operating rod36 again has a member 120 fixed thereto by the pin 118 and has aconfiguration similar to that of FIGURES 4-6 with a groove 122 thereinpartially seating a garter spring 216 of the tension type. The couplingmember generally designated by the numeral 288 is generally similar inconstruction to that of the prior embodiment except that a dependingboss 282 is provided thereon and slots 280- are milled in the sidesthereof normally to the longitudinal axis of the rod 36 and in alignmentwith the location of the groove 214 therein.

In this embodiment, a flat strip type metal spring of generally U-shapedconfiguration and generally designated by the numeral 300 has its baseor web portion 302 fastened to the boss 282 of the coupling member 288by the threaded member 304. The elongated legs 306, 308 of the spring300 are deformed inwardly intermediate their length to provide convexlyarcuate portions 310, 312 bearing against the circumference of thegarter spring 216 exposed by the slots 280 in the sides of the couplingmember 280. A counterweight 314 is carried by a web or weight mountingspring 316 of generally V-shaped configuration extending between thelegs 306, 308 of the sheet metal spring 300 adjacent the upper endsthereof. The Y-type connection enables variation in the spacing of theends of the branches of the Y and thereby the spacing between thte upperends of the legs 306, 308.

As shown in FIGURE 9, the counterweight 314 and V-shaped web spring 316are disposed towards the solenoid and away from the contacts. In theevent of forces of acceleration normally tending to disengage thecoupling by reason of the relative action of inertia upon the severalmembers, the accelerating forces act on the counterweight 314 to producedeflection of the web spring 316 as shown in phantom line in FIGURE 10to pull the upper ends of the legs 306, 308 together. This in turncauses the arcuate portions 310, 312 to bear against the garter spring216 with greater pressure to resist the tendency for expansion of thegarter spring 216 and uncoupling of the connection.

By proper selection of the mass of the counterweight 314 and selectionof stock for and configuration of the springs 300 and 316, the forces ofacceleration acting on the counterweight 314 can substantially equalthose produced by acceleration acting on the remaining members andtending to produce uncoupling. Thus, proper operation of thedisengageable connection will occur even during periods of accelerationor deceleration. Moreover, the biasing pressure exerted by the springlegs 306, 308 can be utilized to determine the force required to beexerted by the solenoid to effect disengagement of the garter spring 216not only at times of acceleration but also during periods of rest orconstant speed. i

The counterbalance embodiment of FIGURES 8-10 is especially advantageousfor vehicles or for military applications where the circuit interrupteris mounted on an element subject to forces of acceleration such as a gunplatform or carriage. Assuming that the breaker were rated for normaloperation at amperes with a trip rating of 500 amperes and assuming acurrent of 450 amperes were flowing therethrough, it can be seen thatthe force being exerted by the solenoid tending to disengage thecoupling is almost sufficient to effect tripping. If acceleration nowoccurs, it is likely that the inertia acting on the elements of thenormal operating mechanism Wlll now cooperate with the solenoid force inovercoming the force of the spring member and produce spurious trippingof the breaker which could be highly disadvantageous from the standpointof operation of a vehicle or of military equipment. By providing thecounterbalance assembly, the same acceleration forces act to increasethe pressure required to disengage the spring member so that tripping ofthe breaker is left essentially solely to the action of the solenoid andthereby to calibrated action.

Although both of the illustrated embodiments utilize tension springs, itwill be appreciated that compression springs may also be utilized in thepresent invention by reversing the arrangement of grooves or recesses inthe cooperating members so that the inner member is of a depth toreceive sufiicient of the thickness of the spring member uponcompression thereof to release the coupling member. Moreover, it shouldalso be appreciated that two or more spring members may be seated incooperating recesses in the coupling and contact carrying members topermit variation in the solenoid force required to effect disengagementor variation in the nature and dimensioning of the several elements.

Other types of spring members may be utilized such as expansible bandsand synthetic and natural elastomers may also be employed. However,coiled metallic garter springs of the type illustrated are preferred forthe present application since they are readily adaptable to closeadjustment in spring power and tend to provide predictable operationover a wide range of temperatures. Moreover, the arcuate surface of thecoil affords some camming action to facilitate uncoupling and minimizessurface friction as the spring member and released member slide relativeto each other.

The recesses for receiving the spring member may assume a variety ofcross-sections so long as they permit the spring member to move relativethereto. They may be annular grooves extending about the entireperiphery of the members as illustrated in the embodiment of FIG- URES1-7 or extend only partially about the member as illustrated withrespect to the coupling member of the embodiment of FIGURES 810. Inaddition, a plurality of pairs of ribs spaced about the periphery of themember may provide suitable spaces or recesses therebetween. The recessor groove in the one member is preferably of a depth to receive the fullthickness of the spring member when it is deflected, thereby permittingsnug fitting of the coupling member and the contact operating rod or itssleeve member 120 to prevent any axial misalignment. However, if someradial clearance is provided between the two coupled members, then thedepth of the groove or recess required to accept the spring member foruncoupling is reduced accordingly.

By utilizing a hollow or tubular contact operating rod and lightweightmaterial for the sleeve member, the inertia of the uncoupled subassemblymay be minimized to enhance the rapidity with which the contacts may beopened. In the illustrated embodiment, a shoulder is provided tocooperate with the spring member in the automatically operated positionto hold the contact operating rod against reclosing or bouncing back. Inplace of such a shoulder, a second groove or recess can be provided inthe released member to receive the spring member in the open contactposition.

Similarly, the counterbalance embodiment is also variable in the natureof its components. If a compression spring is employed for thedisengageable coupling, then the counterbalance mechanism may employ apair of spring members spaced axially to opposite sides of the legs ofthe spring member with relatively rigid connectors extendingtherebetween inwardly of the spring member. In such a version, theV-shaped spring and counterweight should be reversed in orientation withrespect to their disposition relative to the contacts from thearrangement shown in the embodiment of FIGURES 8-10. Thus the force ofacceleration will cause the effective length of the spring to expand anddeflect the arms of the spring outwardly which, in turn, causes anincrease in force necessary to compress the spring sufliciently toproduce decoupling.

Other types of manual operating mechanisms may also be employed inaccordance with the present invention including the type having areleasable cradle or other means for achieving automatic opening of themovable contact without disengagement of the coupling means. In theinvention in this form, therefore, as in the aforesaid patent 3,384,846,there would be manually operable means for opening and closing thecontacts, first automatic means for opening the contacts by automaticoperation of the manually operable mechanism, and second automaticopening means (such as solenoid for opening the contacts independentlyof the manual operating means.

Although the present invention may be utilized in any circuitinterrupter where extremely rapid opening of the contacts is desiredupon passage of a high short circuit current therethrough, it isparticularly advantageously employed in current limiting type circuitbreakers, where almost instantaneous opening of the contacts is desired.

Thus it can be seen that the present invention provides a novel circuitbreaker capable of rapidly opening the contacts independently ofoperation of the manual operating mechanism. The devices may be simplpand relatively economically constructed and are readily adapted tovariation in the magnitude of the short circut current required toeffect uncoupling such as by adjusting the number of turns of thesolenoid or by adjusting the force of the garter spring. By use of thecounterbalance principle herein disclosed, the present invention ishighly effective to ensure precise operation even in applications wherethe interrupter is subjected to accelerational forces when handling acurrent approaching the trip value.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an electric circuit interrupter, comprising:

(a) a casing;

(b) a stationary contact in said casing;

(c) a movable contact in said casing;

(d) a contact operating member carrying contact at one end thereof;

(e) means mounting said contact operating member in said casing formovement of said movable contact between closed and opened positions;

(f) automatic operating means connected to said contact operating memberfor moving said contact operating member from closed to open circuitposition upon passage of a current of predetermined magnitudetherethrough;

(g) manual operating means; and

(h) means coupling said manual operating means to said contact operatingmember for moving said contact operating member between closed and opencircuit positions, said coupling means including a coupling member aboutsaid contact operating member, means engaging said coupling member andsaid manual operating means for translation of movement thereby, and adisengageable connection between said coupling member and contactoperating member including a spring member of generally toroidalconfiguration encircling said contact operating member and being capableof resilient variation in its diameter, the opposed surfaces of saidcoupling member and said contact operating member having alignedrecesses therein each partially receiving said spring the combinationsaid movable member in the normal operative position thereof to providea connection therebetween for operation of said contact operating memberupon movement of said manual operating means, one of said members havingits recess of a depth to completely receive said spring member upondeflection of said spring member to permit relative movement betweensaid coupling member and said contact operating member.

2. The circuit interrupter of claim 1 wherein said spring member is acoiled spring of toroidal configuration.

3. The circuit interrupter of claim 1 wherein said recesses in saidcoupling and contact operating members are provided by generally annulargrooves in the surface thereof.

4. The circuit interrupter of claim 1 wherein said spring member is acompression spring and wherein said contact operating member has arecess of a depth to receive the thickness of the annular spring membernormally biased into the recess of said coupling member.

5. The circuit interrupter of claim 1 wherein said spring is a tensionspring and wherein said coupling member has a recess of a depthsufiicient to receive the thickness of the annular spring membernormally biased into the recess of the contact operating member.

6. The circuit interrupter of claim 1 wherein said other member isshaped to provide means for engagement with said toroidal spring memberin the open circuit position for holding said contact operating memberin open circuit position.

7. The circuit interrupter of claim 6 wherein said means is a generallyannular shoulder on said other memher.

8. The circuit interrupter of claim 1 wherein said automatic operatingmeans includes a solenoid in said casing and a solenoid plunger on saidcontact operating member attractable by said solenoid upon passage of acurrent of sufficient magnitude therethrough to overcome the force ofsaid spring member.

9. The circuit interrupter of claim 1 wherein said coupling meansincludes counterbalancing means subject to accelerational forces toincrease the pressure required to be exerted upon said spring member fordeflection outwardly from the recess of said other member to disengagethe connection between said coupling member and said contact operatingmember.

10. The circuit interrupter of claim 9 wherein said counterbalancingmeans includes auxiliary spring means carried by said coupling memberand having elongated leg portions extending normally to the axis of saidcontact operating member, a generally V-shaped web spring extendingbetween said legs adjacent the upper end thereof and a weight on saidweb spring to produce deflection of said web spring and thereby the legsof said auxiliary spring means, said deflection of said auxiliary springmeans acting to increase the pressure required to deflect said annularspring outwardly from the recess of said other member.

11. The circuit interrupter of claim 10 wherein said toroidal springmember is a tension spring and said one member having said recess of adepth to receive the thickness of the spring member is said couplingmember and wherein said coupling member has apertures communicating withthe recess therein and receiving the leg portions of said auxiliaryspring means intermediate their length, said leg portions of saidauxiliary spring means bearing against the outer periphery of saidtoroidal spring member during acceleration as a result of contraction ofthe spacing between the ends thereof through action of accelerationalforces on said weight carried by the Web spring.

12. The circuit interrupter of claim 11 wherein said leg portions ofsaid auxiliary spring means have convexly arcuate portions intermediatetheir length generally conforming to the periphery of said annularspring member.

13. The circuit interrupter of claim 10' wherein said annular springmember is a compression spring and wherein said one member having arecess of a depth to receive the thickness of the annular spring memberis said contact operating member and wherein said auxiliary spring meanscomprises a pair of spring elements each having leg portions to oppositesides of said coupling member and relatively rigid elements extendingtherebetween axially of said contact operating member and inwardly ofsaid annular spring member, said weight producing expansion in spacingbetween the ends of said leg portions of said spring elements andthereby an outward pressure acting against said annular spring memberduring accelerational force.

References Cited UNITED STATES PATENTS 1,837,185 12/1931 Jones 200772,386,162 10/1945 Hetherington 20077 3,012,118 12/1961 Edmunds 3356BERNARD A. GILHEANY, Primary Examiner H. BROOME, Assistant Examiner U.S.Cl. X.R.

ZOO-77; 335-16, 186

